What’s arguably the finest era of the long-running Doctor Who TV series comes to a close as we bid farewell to the tenth doctor, David Tennant, who makes way for an 11th Doctor — and a new production team for the British science-fiction program.

Helmed by writer-producer Russell Davies for the past four years, after several years off the air, Doctor Who returned with new inspiration and vision in 2005, with Christopher Eccleston as a tough, brooding, leather-jacketed man-of-action ninth doctor in the series’s history.  In shorthand history, the Doctor is a long-lived alien, a Time Lord from the planet Gallifrey who travels in time in his TARDIS, frequently with companions. When critically injured, he can regenerate his body, but, in doing so, gains a new physical appearance and with it a distinct new personality, giving us all the different Doctors over the decades.  Eccleston’s doctor was a survivor of a Time War in which he wiped out both his race and the enemy Daleks. His first companion is Rose (Billie Piper), which eventually leads down the road to a romance. Eccleston’s Doctor also travels for a time with boy-genius Adam (Bruno Langley) and 51st century con-man and former ‘Time Agent’ Captain Jack Harkness (John Barrowman), who turns heroic eventually and spins off into the excellent Torchwood series from Davies.   The ninth doctor sacrifices himself to save Rose, and then regenerates into the tenth doctor — Tennant.

With credits that include a stint with the Royal Shakespeare Company, Tennant’s Tenth Doctor has proven to be warm and fuzzy yet also quite calculating, emotional, and even ruthless when dealing with adversaries and enemies. Tennant may have been the most beloved Doctor of all, carried by Davies’s vision. In a 2009 Doctor Who Magazine readers poll, he was voted as Number One in a Favorite Doctor poll, winning 25.64 percent of the vote, beating out cuddly and long-running ’60s/’70s Fourth Doctor Tom Baker, who came in at number 2 with 24.73 percent of votes.

The tenth doctor’s first companion was Rose, where the romance between them blossomed, but circumstances separated them. They would later be reunited, sort of, as Rose gets a half-human duplicate who’s nearly identical to share a life together.  Other companions included Martha Jones (Freema Agyeman) and Donna Noble (Catherine Tate), though by the end of the 2008 series finale, “Journey’s End,” the Doctor has now a regular companion again. And now, Tennant’s tenure has come to an end, with an 11th doctor, the quite boyish-looking Matt Smith, waiting in the wings, with Stephen Moffat as the show-runner.

Meanwhile, the Davies Tennant farewell is a big one, having included a moving Christmas special last year, “The Next Doctor,” a special earlier this year, “Planet of the Dead,” and continuing with this (past) weekend’s “Waters of Mars,” in which the Doctor appears some 50 years from our current era to witness a catastrophic event on the Red Planet. Should he come to the aid of the Mars base crew as it’s a pivotal event in human space exploration history? Or what if he was part of the events all along? Such are the dilemmas of time travel and such. It’s quite the horror-show episode, even a bit creepy.

The end of the year will see the final, two-part Christmas-time and New Year’s weekend BBC and BBC America airings of “The End of Time.”  According to some [SPOILER ALERT] plot points, the Doctor’s nemesis The Master is reborn on Christmas Eve and battles rage across the wastelands of London and at the mysterious Immortality Gate, while the Ood warn of a danger that threatens the entire universe.  Tension mounts and things get even worse — The Doctor faces the end of his life, as he and Wilf must fight alone and the prophecy warns: “He will knock four times.”  Earlier this year, Davies told Buzzine it’s an epic and grand and quite tear-streaked goodbye to the Tennant era.  And what an era it’s been.  Tennant and Davies will both be missed, but the Doctor carries on — so does a legacy of Doctors going back to the start of this series more than 45 years ago,  now cherished around the globe.